System and Method for Purging Reductant in a Reductant Dosing System

ABSTRACT

A reductant supply system includes a pump having a suction side and a discharge side, and a tank that holds a reductant therein. A reductant supply passageway extends from the tank to the suction side of the pump so as to supply the reductant from the tank to the pump. Further, a reductant discharge passageway extends from the discharge side of the pump and is configured to supply the reductant to a reductant injection assembly that injects the reductant into an exhaust stream of an engine. The system further includes purge componentry that connects the reductant supply passageway to an ambient air source during a purging operation such that the reductant supply system draws air from the air source sequentially through the purge passageway, the reductant supply passageway, and the pump assembly to purge at least the reductant supply passageway and the pump assembly during the purging operation.

TECHNICAL FIELD

The present disclosure relates to the treatment of exhaust gases generated by internal combustion engines, and more specifically to reductant dosing systems and methods.

BACKGROUND

Reductant dosing systems are typically used to reduce nitrogen oxide (NO_(x)) emissions in large machines where space and weight considerations are not a concern, such as, for example, in locomotives and stationary power generation applications. The reductant is stored in a tank located on the machine and, as the machine operates and produces exhaust, the reductant is pumped from the tank into the machine's exhaust system. The reductant reacts with exhaust at high temperatures to affect a selective catalytic reduction (SCR) of NOx within the exhaust.

A possible shortcoming of dosing systems relates to the ambient temperatures at which some reductants freeze (about 12° F.). When the reductant freezes, it may expand within the dosing system, possibly causing damage to and/or clogging of intricate components such as injector nozzles. One way to inhibit freezing is to purge the system after use.

U.S. Pat. No. 8,291,926 (the '926 patent) by Thiagarajan et al. discloses an exemplary reductant dosing system. Specifically, the '926 patent discloses a reductant storage tank that is connected to an exhaust system via a pump and a passageway. Reductant is injected into the exhaust system via an injection device located on the passageway. The '926 patent also discloses a purging system that purges reductant from at least a portion of the passageway using compressed air.

SUMMARY

In one aspect, a reductant supply system comprises a tank and a pump assembly. The tank defines a cavity configured to hold a reductant therein. The pump assembly has a suction side that is fluidly coupled to the tank, and has a discharge side that is configured to fluidly couple to a reductant injection assembly that injects the reductant into an exhaust stream of an engine. The reductant supply system further comprises a reductant supply passageway and a purge passageway. The reductant supply passageway extends from the tank to the suction side of the pump assembly so as to fluidly couple the tank to the pump assembly. The purge passageway is connected to the reductant supply passageway between an inlet of the reductant supply passageway and the pump assembly. Further, the purge passageway is configured to selectively couple the pump assembly to an ambient air source during a purging operation such that the pump assembly draws air from the ambient air source through the reductant supply passageway and the pump assembly during the purging operation to purge the reductant supply passageway and the pump assembly.

In another aspect, a reductant supply system comprises a reductant dosing cabinet. The reductant dosing cabinet comprises a local tank and a pump assembly. The local tank defines a cavity that is configured to hold a reductant therein. The pump assembly has a suction side and a discharge side. The suction side that is fluidly coupled to the local tank, and the discharge side is configured to fluidly couple to a reductant injection assembly that injects the reductant into an exhaust stream of an engine. The reductant dosing cabinet further comprises a reductant replenishment passageway configured to fluidly couple the local tank to a reductant replenishment assembly so as to replenish the reductant in the local tank, wherein the reductant replenishment assembly is spaced from, and external to, the reductant dosing cabinet. The reductant dosing cabinet yet further comprises a reductant return passageway that is configured to selectively couple the discharge side of the pump to the reductant replenishment assembly during a purge operation so as to return the reductant from both the local tank and the pump to the reductant replenishment assembly during the purge operation.

Yet another aspect is a method of purging reductant from a reductant dosing cabinet. The method comprises coupling the reductant dosing cabinet to a reductant injection assembly that injects the reductant into an exhaust stream of an engine and to a reductant replenishment assembly that is spaced from, and external to, the reductant dosing cabinet. The reductant dosing cabinet comprises a local tank and a pump assembly. The local tank defines a cavity configured to hold a reductant therein. The pump assembly has a suction side that is fluidly coupled to the local tank, and has a discharge side that is selectively connectable to the reductant injection assembly. The method further comprises fluidly coupling the discharge side of the pump assembly to the reductant replenishment assembly, and operating the pump assembly so as purge the reductant in the local tank and the pump assembly to the reductant replenishment assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of embodiments of the application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the methods and apparatuses of the present application, there is shown in the drawings representative embodiments. It should be understood, however, that the application is not limited to the precise methods and apparatuses shown. In the drawings:

FIG. 1 shows a simplified schematic diagram of a reductant supply system according to one embodiment;

FIG. 2 shows a simplified schematic diagram of a reductant supply system according to another embodiment;

FIG. 3 shows a simplified schematic diagram of a reductant supply system according to yet another embodiment; and

FIG. 4 shows a simplified schematic diagram of an engine system including a reductant supply system according to one embodiment.

DETAILED DESCRIPTION

Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, “left”, “lower” and “upper” designate directions in the drawings to which reference is made. The words “inner” or “distal” and “outer” or “proximal” refer to directions toward and away from, respectively, the engine and related parts thereof. The terminology includes the above-listed words, derivatives thereof and words of similar import.

As a general overview, reductant supply systems and methods of operating the same are disclosed herein. Each reductant supply system includes dosing componentry and is selectively configurable to perform dosing operations, whereby the dosing componentry supplies the reductant to an engine exhaust stream. For example, the dosing componentry can include a local tank configured to store reductant, reductant passageways fluidly coupling the local tank to a reductant injection assembly that injects the reductant into an engine exhaust stream, and a pump assembly configured to draw the reductant from the local tank and supply the reductant to the reductant injection assembly via the reductant passageways. Further, each reductant supply system includes purge componentry and is selectively configurable perform purging operations, whereby the purge componentry is used to purge reductant from the dosing componentry.

Referring to FIGS. 1 to 3, simplified schematic diagrams of reductant supply system 100, 100′, and 100″ according to various embodiments are shown. Each reductant supply system 100, 100′, and 100″ is configured to supply reductant, such as (without limitation) liquid urea or ammonia, to an exhaust stream of an engine. Each reductant supply system 100, 100′, and 100″ includes a reductant dosing assembly 102, 102′, and 102″. Further, each reductant supply system 100, 100′, and 100″ can include one or more of a reductant injection assembly 104, a compressed gas assembly 106, and a reductant replenishment assembly 108, each in fluid communication with the reductant dosing assembly 102, 102′, and 102″.

It will be understood that, in some embodiments, the reductant supply system 100, 100′, and 100″ can include only the reductant dosing assembly 102, 102′, and 102″, while in other embodiments, the reductant supply system 100, 100′, and 100″ can include the reductant dosing assembly 102, 102′, and 102″ and one or more of the reductant injection assembly 104, the compressed gas assembly 106, and the reductant replenishment assembly 108. As will be described in further detail below, reductant supply systems 100, 100′, and 100″ are generally similar to one another. However, each reductant supply system 100, 100′, and 100″ includes different reductant purge componentry configured to purge reductant within the reductant dosing assembly 102, 102′, and 102″ to prevent freezing of the reductant.

Each reductant dosing assembly 102, 102′, and 102″ includes a reductant dosing cabinet 110 that houses or otherwise supports the components of the reductant dosing assembly 102, 102′, and 102″. Thus, each reductant dosing assembly 102, 102′, and 102″ can be referred to as a reductant dosing cabinet, although alternative embodiments are not limited to cabinets. Each reductant dosing cabinet 110 includes at least one wall 112 having an interior surface 112 a and an exterior surface 112 b. The interior surface 112 a defines a cavity 113 in which the components of the reductant dosing assembly 102, 102′, and 102″ are housed. Each reductant dosing assembly 102, 102′, and 102″ includes at least one, such as a plurality of ports 150, 164, 170, and 178, each of which provides a passageway through the at least one wall 112 from an interior of the reductant dosing cabinet 110 to an exterior of the reductant dosing cabinet 110. The ports 150, 164, 170, and 178 may be supported by, or otherwise mounted to, at least one of the interior surface 112 a, the exterior surface 112 b, and an inner surface of the at least one wall 112 that extends between the internal and exterior surfaces 112 a and 112 b and defines an opening through the at least one wall 112. Each port can include a coupling that is configured so as to enable the reductant dosing assembly 102, 102′, and 102″ to be removably connectable to, and placed in fluid communication with, one of the reductant injection assembly 104, the compressed gas assembly 106, and the reductant replenishment assembly 108. Thus, the reductant dosing assembly 102, 102′, and 102″ can be a separable, self-contained unit that can be installed in various engines and various reductant supply systems.

Each reductant dosing assembly 102, 102′, and 102″ includes the local tank 114 and a dosing pump assembly 138 housed within, or otherwise supported by, the reductant dosing cabinet 110. Each reductant dosing assembly 102, 102′, and 102″ can further include a reductant supply passageway 132, a reductant discharge passageway 162, a reductant replenishment passageway 146, and a compressed gas supply passageway 172 housed within, or otherwise supported by, the reductant dosing cabinet 110. However, in alternative embodiments, one or more of these components may be omitted (e.g., when one or both of the compressed gas assembly 106 and the reductant replenishment assembly 108 is omitted).

The local tank 114 of each reductant dosing assembly 102, 102′, and 102″ defines a local tank cavity 116 having a maximum volume that is configured to hold the reductant. The local tank 114 can also include a tank manifold 120 that supports or defines a reductant supply port 124 and a reductant replenishment inlet port 126 (in embodiments that employ the reductant replenishment assembly 108). In at least some embodiments, the tank manifold 120 is supported by an upper, exterior surface 112 b of the local tank 114. The local tank 114 can also include a vent 118, a level sensor 122, a heater 128, and a manual fill port 130, although one or more of these components can be omitted.

In each reductant dosing assembly 102, 102′, and 102″, the reductant supply passageway 132 fluidly couples the local tank 114 to the dosing pump assembly 138 such that the reductant supply passageway 132 supplies reductant from the local tank 114 to the dosing pump assembly 138. The reductant supply passageway 132 extends between the local tank 114 and the dosing pump assembly 138, and in at least some embodiments, the reductant supply passageway 132 can extend from the reductant supply port 124 of the local tank 114 to a suction side 138 a of the dosing pump assembly 138. Further, in at least some embodiments, the reductant supply passageway 132 can extend through the reductant supply port 124 on the tank manifold 120 into the local tank 114, and terminate at a bottom portion of the local tank cavity 116.

The dosing pump assembly 138 of each reductant dosing assembly 102, 102′ pumps the reductant from the local tank 114 in a first direction that extends from the local tank 114 to the reductant injection assembly 104. The dosing pump assembly 138 has an inlet or suction side 138 a and an outlet or discharge side 138 b. The suction side 138 a is fluidly coupled to the local tank 114, and the discharge side 13 b is configured to fluidly couple to the reductant injection assembly 104. Further, the dosing pump assembly 138 includes a pump 140 and first and second check valves 142 and 144 in fluid communication with the pump 140, although in alternative embodiments, one or both of the first and second check valves 142 and 144 can be omitted. Each of the first and second check valves 142 and 144 permits flow of reductant in the first direction and limits or prevents flow of the reductant in a second direction, opposite the first direction. The first check valve 142 is fluidly coupled to the pump 140 at the suction side 138 a of the dosing pump assembly 138, between the local tank 114 and the pump 140, so as to limit or prevent flow of the reductant in the second direction from the pump 140 back toward the local tank 114. The second check valve 144 is connected to the pump 140 at the discharge side 138 b of the dosing pump assembly 138, between the pump 140 and the reductant injection assembly 104, so as to limit or prevent flow of the reductant in the second direction from the reductant injection assembly 104 back toward the pump 140.

The reductant discharge passageway 162 of each reductant dosing assembly 102, 102′, and 102″ extends from the discharge side 138 b of the dosing pump assembly 138 to a terminal end of the reductant discharge passageway 162 that includes or terminates at the port 164. The port 164 can include a coupling configured to removably connect the reductant dosing assembly 102, 102′, and 102″ to the reductant injection assembly 104. Thus, when the reductant dosing assembly 102, 102′, and 102″ is connected to the reductant injection assembly 104, the reductant discharge passageway 162 supplies reductant in the first direction to the reductant injection assembly 104. The reductant injection assembly 104 includes an injector 186 and can include a reductant passageway 184 that is removably connectable to the port 164 so as to place the injector 186 in fluid communication with the port 164, the reductant discharge passageway 162, and the reductant dosing assembly 102, 102′, and 102″.

In addition to reductant, compressed gas can also be supplied to the reductant injection assembly 104, where the injector 186 can combine the reductant and compressed gas into a mixture and inject the mixture into the engine exhaust stream. Thus, each reductant dosing assembly 102, 102′, and 102″ can include a compressed gas passageway 172 that fluidly couples the compressed gas assembly 106 to the reductant injection assembly 104. In this embodiment, the compressed gas passageway 172 extends from the port 170 to the port 178 and is defined by, or otherwise supported by, a compressed gas manifold 180 that can be mounted to the at least one wall 112 of the reductant dosing cabinet 110. Thus, the compressed gas passageway 172 can be said to extend to terminate ends of the compressed gas passageway 172 that terminate at or include the ports 170 and 178. Further, the compressed gas passageway 172 includes a gas regulator 174 that regulates the pressure of the compressed gas, and a shutoff valve 176, both of which are situated between the ports 170 and 178. However, in alternative embodiments, one or both of the gas regulator 174 and shutoff valve 176 can be omitted or moved to the compressed gas assembly 106 or the reductant injection assembly 104.

The port 170 can include a coupler that removably connects the compressed gas passageway 172 to the compressed gas assembly 106 so as to place the compressed gas assembly 106 in fluid communication with the compressed gas passageway 172. The compressed gas assembly 106 includes a compressed gas source 190 such as a compressor that pressurizes a gas, and can include a compressed gas passageway 188 that is removably connectable to the port 170. Thus, the compressed gas passageway 188 extends from the compressed gas source 190 to the port 170 so as to supply the compressed gas from the compressed gas source 190 to the reductant dosing assembly 102, 102′, and 102″.

Similarly, the port 178 can include a coupler that removably connects the compressed gas passageway 172 to the reductant injection assembly 104 so as to place the reductant injection assembly 104 in fluid communication with the compressed gas passageway 172. The reductant injection assembly 104 can include a compressed gas passageway 182 that is removably connectable to the port 178 and that extends from the port 178 to the injector 186 so as to supply the compressed gas from the reductant dosing assembly 102, 102′, and 102″ to the injector 186.

As the reductant from the local tank 114 depletes in each reductant dosing assembly 102, 102′, and 102″, the reductant in the local tank 114 can be replenished by the reductant replenishment assembly 108. Thus, each reductant dosing assembly 102, 102′, and 102″ can include a reductant replenishment passageway 146 that is configured to fluidly couple the reductant replenishment assembly 108 to the local tank 114 so as to replenish the reductant in the local tank 114. As shown, the reductant replenishment assembly 108 is spaced from, and external to, the reductant dosing cabinet 110.

In the embodiments of FIGS. 1 to 3, the reductant replenishment passageway 146 extends from the port 150 to the reductant replenishment inlet port 126 of the local tank 114 and includes a shutoff valve 148. Thus, the reductant replenishment passageway 146 can be said to extend from the local tank 114 to a terminal end of the reductant replenishment passageway 146 that includes or terminates at the port 150. One or more of the port 150, the port 164, the reductant replenishment passageway 146, and the dosing pump assembly 138 can be defined by, or otherwise supported by, a reductant manifold 158 that can be mounted to the at least one wall 112 of the reductant dosing cabinet 110. The reductant manifold 158 can also include a heater 152 to prevent freezing of any reductant in the manifold.

The port 150 can include a coupler that removably connects the reductant replenishment assembly 108 to the reductant replenishment passageway 146. The reductant replenishment assembly 108 includes a remote tank 192, a reductant passageway 194, and a replenishment pump 196. The remote tank 192 is spaced from the reductant dosing assembly 102, 102′, and 102″ and defines a cavity having a maximum volume that is configured to hold the reductant therein, wherein the maximum volume of the remote tank 192 is greater than the maximum volume of the local tank 114 and can further be greater than a maximum volume of the cavity 113 of the reductant dosing cabinet 110. The reductant passageway 194 is removably connectable to the port 150, and extends from the remote tank 192 to the port 150. The replenishment pump 196, which is connected to or is a part of the reductant passageway 194, pumps the reductant from the remote tank 192 to the reductant dosing assembly 102, 102′, and 102″ via the reductant passageway 194 so as to replenish or refill the local tank 114.

When the environmental temperature surrounding each reductant dosing assembly 102, 102′, and 102″ drops below the freezing temperature of the reductant, any reductant remaining in the reductant dosing assembly 102, 102′, and 102″ can freeze. Freezing of the reductant can inhibit the reductant dosing assembly 102, 102′, and 102″ from providing reductant to the reductant injection assembly 104 and can even result in the cracking of various components of the reductant dosing assembly 102, 102′, and 102″ such as the pump assembly 138. Therefore, to reduce the likelihood of freezing, each reductant dosing assembly 102, 102′, and 102″ also includes reductant purge componentry that is configured to purge various components of the reductant dosing assembly 102, 102′, and 102′.

Referring specifically to FIG. 1, the reductant purge componentry of the reductant dosing assembly 102 includes a reductant return passageway 154 and a purge passageway 134. The reductant return passageway 154, which can be defined by or otherwise supported by the reductant manifold 158, extends from the reductant discharge passageway 162 at a location that is between the dosing pump assembly 138 and the port 164, and extends to the reductant replenishment passageway 146 at a location that is between the local tank 114 and the port 150. The reductant return passageway 154 includes a shutoff valve 156 that selectively permits and inhibits flow of the reductant from the reductant discharge passageway 162 to the reductant replenishment passageway 146.

The purge passageway 134, which can be defined by or otherwise supported by the tank manifold 120, extends from the reductant supply passageway 132 between an inlet of the reductant supply passageway 132 and the dosing pump assembly 138, and extends to an ambient air source such as the environment adjacent the purge passageway 134. In at least some embodiments, the purge passageway 134 can extend from the reductant supply passageway 132 between the local tank 114 and the dosing pump assembly 138. The purge passageway 134 includes a shutoff valve 136 that selectively permits and inhibits flow of ambient air from the environment to the reductant supply passageway 132. Thus, the purge passageway 134 is configured to selectively couple the pump assembly 138 to the ambient air source during a purging operation such that the pump assembly 138 draws air from the ambient air source through the reductant supply passageway 132 and the pump assembly 138 during the purging operation to purge the reductant supply passageway 132 and the pump assembly 138. As will be understood, the purge passageway 134 can include alternative componentry such as a three-way valve at the junction of the reductant supply passageway 132 and the purge passageway 134.

Before operating the reductant dosing cabinet 110, the reductant dosing cabinet 110 is coupled to at least one, such as all, of the reductant injection assembly 104, the compressed gas assembly 106, and the reductant replenishment assembly 108. During dosing operations, the local tank 114 and compressed gas assembly 106 are fluidly coupled to the reductant injection assembly 104. In particular, the shutoff valve 176 is in an open position such that compressed gas flows through the shutoff valve 176 to the injector 186, and the shutoff valve 148 can be in an open position so that reductant can be pumped from the remote tank 192 to the local tank 114 as the reductant in the local tank 114 depletes. Further, the shutoff valve 156 can be in a closed position so as to prevent reductant from returning to the local tank 114, and the shutoff valve 136 can be in a closed position so as to prevent ambient air from being drawn into the reductant supply passageway 132 via the purge passageway 134.

During purging operations, residual reductant in the reductant dosing assembly 102 can be purged in two stages. In one stage, which can be for example the first stage, the reductant discharge passageway 162 is fluidly coupled to the local tank 114 via the reductant return passageway 154. In particular, the shutoff valves 148 and 136 are in closed positions, the shutoff valves 176 and 156 are in open positions, and the pump 140 is turned off. Compressed gas from the compressed gas source 190 flows through the compressed gas passageway 172 to the reductant injection assembly 104, and some or all of the compressed gas flows back into the reductant discharge passageway 162 toward the pump assembly 140 in a second direction, opposite the first direction. As the compressed gas flows into the reductant discharge passageway 162, the compressed gas forces the reductant out of the reductant discharge passageway 162 and back to the local tank 114 via the reductant return passageway 154, thereby leaving the reductant discharge passageway 162 substantially devoid of residual reductant.

In the other stage, which can be for example the second stage, the shutoff valves 148 and 176 are in closed positions, the pump assembly 138 is fluidly connected to the ambient air source. In particular, the shutoff valves 136 and 156 are in open positions, and the pump 140 is turned on. The pump 140 draws ambient air through the purge passageway 134, through the reductant supply passageway 132 and the pump assembly 138, and forces the ambient air out the discharge side 138 b of the pump assembly 138 back to the local tank 114 via the reductant return passageway 154. As the ambient air flows through the reductant supply passageway 132, the pump assembly 138, and the reductant return passageway 154, the ambient air forces the reductant out of the reductant supply passageway 132, the pump assembly 138, and the reductant return passageway 154 and back to the local tank 114, thereby leaving the reductant supply passageway 132, the pump assembly 138, and the reductant return passageway 154 substantially devoid of residual reductant.

Referring now to FIG. 2, the reductant purge componentry of the reductant dosing assembly 102′ includes a reductant return passageway 154 as described above in relation to FIG. 1, and a purge passageway 200. The purge passageway 200 extends from the compressed gas passageway 172 between the port 170 and the port 178, and extends to the reductant supply passageway 132 between an inlet of the reductant supply passageway 132 and the pump assembly 138. In at least some embodiments, the purge passageway 200 can extend from the reductant supply passageway 132 between the local tank 114 and the dosing pump assembly 138. The purge passageway 200 includes a shutoff valve 202 that selectively permits and inhibits flow of the compressed gas from the compressed gas assembly 106 to the reductant supply passageway 132. As will be understood, the purge passageway 200 can include alternative componentry such as a three-way valve at the junction of the compressed gas passageway 172 and the purge passageway 200.

Before operating the reductant dosing cabinet 110, the reductant dosing cabinet 110 is coupled to at least one, such as all, of the reductant injection assembly 104, the compressed gas assembly 106, and the reductant replenishment assembly 108. During dosing operations, the shutoff valve 176 is in an open position and the shutoff valve 202 is in a closed position such that compressed gas flows through the shutoff valve 176 to the injector 186. The shutoff valve 148 can be in an open position so that reductant can be pumped from the remote tank 192 to the local tank 114 as the reductant in the local tank 114 depletes. Further, the shutoff valve 156 can be in a closed position so as to prevent reductant from returning to the local tank 114.

During purging operations, residual reductant in the reductant dosing assembly 102 can be purged in two stages. In one stage, which can be for example the first stage, the reductant discharge passageway 162 is fluidly coupled to the local tank 114 via the reductant return passageway 154. In particular, the shutoff valves 148 and 202 are in closed positions, the shutoff valves 176 and 156 are in open positions, and the pump 140 is turned off. Compressed gas from the compressed gas source 190 flows through the compressed gas passageway 172 to the reductant injection assembly 104, and some or all of the compressed gas flows back into the reductant discharge passageway 162 toward the pump assembly 140 in a second direction, opposite the first direction. As the compressed gas flows into the reductant discharge passageway 162, the compressed gas forces the reductant out of the reductant discharge passageway 162 and back to the local tank 114 via the reductant return passageway 154, thereby leaving the reductant discharge passageway 162 substantially devoid of residual reductant.

In the other stage, which can be for example the second stage, the shutoff valves 148 and 176 are in closed positions, the shutoff valves 156 and 202 are in open positions. Further, the pump 140 is turned off, although in alternative embodiments, the pump 140 can be left on. The compressed gas flows through the purge passageway 200, through the reductant supply passageway 132 and the pump assembly 138, and out the discharge side 138 b of the pump assembly 138 back to the local tank 114 via the reductant return passageway 154. As the compressed gas flows through the reductant supply passageway 132, the pump assembly 138, and the reductant return passageway 154, the compressed gas forces the reductant out of the reductant supply passageway 132, the pump assembly 138, and the reductant return passageway 154 and back to the local tank 114, thereby leaving the reductant supply passageway 132, the pump assembly 138, and the reductant return passageway 154 substantially devoid of residual reductant.

Referring now to FIG. 3, the reductant purge componentry of the reductant dosing assembly 102″ includes a reductant return passageway 154 as described above in relation to FIG. 1, and a purge passageway 300. The purge passageway 300 is configured to selectively couple the discharge side 138 b of the pump assembly 138 to the reductant replenishment assembly 108 during a purge operation so as to return the reductant from both the local tank 114 and the pump assembly 138 to the reductant replenishment assembly 108 during the purge operation. The purge passageway 300 extends from the reductant discharge passageway 162 between the pump assembly 138 and the port 164, and extends to a port 306. The port 306 provides a passageway through the at least one wall 112 of the reductant dosing cabinet 110 from an interior of the reductant dosing cabinet 110 to an exterior of the reductant dosing cabinet 110. The port 306 may be supported by, or otherwise mounted to, at least one of the interior surface 112 a of the reductant dosing cabinet 110, the exterior surface 112 b, and an inner surface of the at least one wall 112 that extends between the internal and exterior surfaces 112 a and 112 b and defines an opening through the at least one wall 112. Further, the port 306 can include a coupling that is configured so as to enable the reductant dosing assembly 102″ to be removably connectable to, and placed in fluid communication with the reductant replenishment assembly 108.

The purge passageway 300 is coupled to the reductant discharge passageway 162 at a junction 302 between the pump assembly 138 and the port 164. The junction 302 includes a diverter valve 304 that is coupled to both the reductant discharge passageway 162 and the purge passageway 300. The diverter valve 304 is selectively configurable to operate in a first or pass-through position that permits flow of the reductant to the reductant injection assembly 104, while inhibiting flow of the reductant to the purge passageway 300, and a second or diverting position that permits flow of the reductant to the purge passageway 300, while inhibiting flow of the reductant to the reductant injection assembly 104. As will be understood, the purge componentry can include devices other than the diverter valve 304 such as a first shutoff valve coupled to the reductant discharge passageway 162 between the junction 302 and the port 164, and a second shutoff valve coupled to the purge passageway 300 between the junction 302 and the port 306.

Before operating the reductant dosing cabinet 110, the reductant dosing cabinet 110 is coupled to at least one, such as all, of the reductant injection assembly 104, the compressed gas assembly 106, and the reductant replenishment assembly 108. During dosing operations, the shutoff valve 176 is in an open position such that compressed gas flows through the shutoff valve 176 to the reductant injection assembly 104, and the diverter valve 304 is in the pass-through position so as to permit flow of the reductant to the reductant injection assembly 104. The shutoff valve 148 can be in an open position so that reductant can be pumped from the remote tank 192 to the local tank 114 as the reductant in the local tank 114 depletes. Further, the shutoff valve 156 can be in a closed position so as to prevent reductant from returning to the local tank 114.

During purging operations, residual reductant in the reductant dosing assembly 102″ can be purged in two or more stages. In one stage, which can be for example the first stage, the reductant discharge passageway 162 is fluidly coupled to the local tank 114 via the reductant return passageway 154. In particular, the shutoff valve 148 is in a closed position, the diverter valve 304 is in the pass-through position, the shutoff valves 156 and 176 are in open positions, and the pump 140 is turned off. Compressed gas from the compressed gas source 190 flows through the compressed gas passageway 172 to the reductant injection assembly 104, and some or all of the compressed gas flows back into the reductant discharge passageway 162 toward the pump assembly 140 in a second direction, opposite the first direction. As the compressed gas flows into the reductant discharge passageway 162, the compressed gas forces the reductant out of the reductant discharge passageway 162 and back to the local tank 114 via the reductant return passageway 154, thereby leaving the reductant discharge passageway 162 substantially devoid of residual reductant.

In another stage, which can be for example the second stage, the discharge side 138 b of the pump assembly 138 is fluidly coupled to the reductant replenishment assembly 108. In particular, the shutoff valves 148 and 176 are in closed positions, the diverter valve 304 is the diverting position, and the shutoff valves 156 is in an open position. Further, the pump 140 is operated such that the reductant in the local tank 114 is drawn through the reductant supply passageway 132 and the pump assembly 138, and is forced out the discharge side 138 b of the pump assembly 138 back to the remote tank 192 via the purge passageway 300. As the local tank 114 empties, ambient air flows into the local tank 114 through the vent 118 to fill the space in the local tank cavity 116 of the local tank 114 that was previously occupied by the reductant.

When most, if not all, of the reductant is purged from the local tank 114, the pump 140 draws the ambient air in the local tank 114 through the reductant supply passageway 132 and the pump assembly 138, and forces the ambient air out of the discharge side 138 b of the pump assembly 138 to the remote tank 192 via the purge passageway 300. As the ambient air flows through the reductant supply passageway 132, the pump assembly 138, the reductant return passageway 154, and the purge passageway 300, the ambient air forces the reductant out of the reductant supply passageway 132, the pump assembly 138, the reductant return passageway 154, and the purge passageway 300, thereby leaving the local tank 114, the reductant supply passageway 132, the pump assembly 138, the reductant return passageway 154, and the purge passageway 300 substantially devoid of reductant. Thus, the entire reductant dosing assembly 102″, including the local tank 114, can be substantially purged of reductant. In at least some embodiments, the first stage of the purge operation can be repeated to further ensure that the entire reductant dosing assembly 102″ is substantially purged of reductant.

INDUSTRIAL APPLICABILITY

Referring to FIG. 4, a simplified schematic diagram of an off-vehicle engine system 400 according to one embodiment is shown that can implement any of the reductant dosing assemblies 102, 102′, and 102″ of FIGS. 1 to 3. The engine system 400 has an engine 402 and an exhaust treatment system. The engine 402 may be, for example, a diesel engine that generates an exhaust stream including gaseous pollutants and solid particulate matter such as soot. The engine 402 has an exhaust outlet, which provides the exhaust stream to the exhaust treatment system. The exhaust treatment system can include various modules that operate to reduce the pollutants in the exhaust stream such as (without limitation) one or more of a diesel oxidation catalyst (DOC) module 404, a diesel particulate filter (DPF) module 406, and a selective catalytic reduction (SCR) module 408.

During operation of the engine 402, the exhaust stream flows from the exhaust outlet of the engine 402 to the DOC module 404, which may include an oxidation catalyst. The oxidation catalyst converts the nitrogen monoxide (NO) components in the exhaust stream to nitrogen dioxide (NO₂) as the exhaust stream passes from the inlet of the DOC module 404 to the outlet of the DOC module 404. The exhaust stream with the converted NO2 flows from the DOC module 404 to the DPF module 406. The DPF module 406 may trap solid particulate matter such as soot, while allowing the gaseous components of the exhaust stream to pass to the outlet of the DPF module 406. The gaseous components of the exhaust stream output from the DPF module 406 are combined with a mixture of reductant and air, which is injected into the exhaust stream by the reductant supply system 100, 100′, and 100″, which includes the reductant injection assembly 104. The exhaust stream with reductant flows to the SCR module 408, which includes an SCR catalyst. The SCR catalyst promotes a reaction between the reductant and nitrogen oxides (NO_(x)) in the exhaust stream to form diatomic nitrogen (N₂) and water (H₂O).

The reductant injection assembly 104 works in tandem with the reductant dosing assembly 102, 102′, and 102″, the compressed gas assembly 106, and the reductant replenishment assembly 108 during operation of the engine 402 to supply the mixture of reductant and air. As described above, the reductant dosing assembly 102, 102′, and 102″ provides compressed gas from the compressed gas assembly 106 to the reductant injection assembly 104 via compressed gas passageway 182 and reductant from the local tank 114 (see FIGS. 1 to 3) to the reductant injection assembly 104 via reductant passageway 184. As the reductant in the local tank 114 depletes, the reductant replenishment assembly 108 supplies the reductant to the local tank 114 of the reductant dosing assembly 102, 102′, and 102″ via the reductant replenishment passageway 146.

When the environmental temperature surrounding each reductant dosing assembly 102, 102′, and 102″ drops below the freezing temperature of the reductant, the reductant dosing assembly 102, 102′, and 102″ performs a purging operation, whereby reductant in the reductant passageways of the reductant dosing assembly 102, 102′, and 102″ is purged to either the local tank 114 of the reductant dosing assembly 102, 102′, and 102″ as described above in relation to FIGS. 1 and 2, or to the reductant replenishment assembly 108 via reductant purge passageway 308 as described above in relation to FIG. 3.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. Furthermore, it should be appreciated that the structure, features, and methods as described above with respect to any of the embodiments described herein can be incorporated into any of the other embodiments described herein unless otherwise indicated. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present disclosure. 

We claim:
 1. A reductant supply system, comprising: a tank defining a cavity, the cavity configured to hold a reductant; a pump assembly having a suction side that is fluidly coupled to the tank, and having a suction side that is configured to fluidly couple to a reductant injection assembly, the reductant injection assembly configured to inject the reductant into an exhaust stream of an engine; a reductant supply passageway that extends from the tank to the suction side of the pump assembly so as to fluidly couple the tank to the pump assembly; and a purge passageway connected to the reductant supply passageway between an inlet of the reductant supply passageway and the pump assembly, the purge passageway configured to selectively couple the pump assembly to an ambient air source during a purging operation such that the pump assembly is configured to draw air from the ambient air source through both the reductant supply passageway and the pump assembly during the purging operation to purge the reductant from the reductant supply passageway and the pump assembly.
 2. The reductant supply system of claim 1, wherein the purge passageway includes a valve that selectively couples the reductant supply passageway to the ambient air source during the purging operation, wherein the ambient air source is an environment outside of the tank.
 3. The reductant supply system of claim 1, further comprising a reductant return passageway that is selectively configurable to return reductant from the suction side of the pump assembly back to the tank during the purge operation.
 4. The reductant supply system of claim 3, further comprising a reductant discharge passageway fluidly coupled to the suction side of the pump assembly, wherein the reductant return passageway is selectively connectable to the reductant discharge passageway between the pump assembly and the reductant injection assembly.
 5. The reductant supply system of claim 1, comprising a cabinet that houses the tank, the pump assembly, the reductant supply passageway, and the purge passageway.
 6. The reductant supply system of claim 5, wherein the cabinet further houses a reductant discharge passageway fluidly coupled to the suction side of the pump assembly, and the reductant discharge passageway includes a port that extends through a wall of the cabinet so as to removably couple the reductant discharge passageway to the reductant injection assembly.
 7. The reductant supply system of claim 5, further comprising a reductant replenishment passageway configured to removably couple the tank to a second tank that is spaced from the cabinet so as to replenish the reductant in the tank.
 8. The reductant supply system of claim 1, further comprising a compressed gas passageway configured to selectively connect a compressed gas source to the reductant injection assembly.
 9. A reductant supply system comprising a reductant dosing cabinet, the reductant dosing cabinet comprising: a tank that defines a cavity, the cavity configured to hold a reductant; a pump assembly having a suction side that is fluidly coupled to the tank and a suction side that is configured to fluidly couple to a reductant injection assembly that injects the reductant into an exhaust stream of an engine; a reductant replenishment passageway configured to fluidly couple the tank to a reductant replenishment assembly so as to replenish the reductant in the tank, wherein the reductant replenishment assembly is spaced from, and external to, the reductant dosing cabinet; and a purge passageway configured to selectively couple the suction side of the pump assembly to the reductant replenishment assembly during a purge operation so as to return the reductant from both the tank and the pump assembly to the reductant replenishment assembly during the purge operation.
 10. The reductant supply system of claim 9, wherein the reductant dosing cabinet includes a reductant discharge passageway fluidly coupled to the suction side of the pump assembly, and the reductant dosing cabinet includes at least one valve that is selectively configurable to supply the reductant to the reductant injection assembly during a dosing operation and divert the reductant to the purge passageway during the purge operation.
 11. The reductant supply system of claim 9, wherein the reductant replenishment passageway includes a port that extends through a wall of the cabinet so as to removably couple the reductant replenishment assembly to the tank.
 12. The reductant supply system of claim 11, wherein the reductant replenishment assembly includes a second tank, spaced from the reductant dosing cabinet, the second tank defining a second cavity that has a maximum volume configured to hold the reductant, wherein the maximum volume of the second tank is greater than a maximum volume of the tank.
 13. The reductant supply system of claim 12, wherein the reductant replenishment assembly includes a pump that is configured to flow the reductant from the second tank to the tank.
 14. The reductant supply system of claim 9, wherein the reductant dosing cabinet further comprises a reductant discharge passageway fluidly coupled to the suction side of the pump assembly, and the reductant discharge passageway includes a port that extends through a wall of the reductant dosing cabinet so as to removably couple the reductant discharge passageway to the reductant injection assembly.
 15. The reductant supply system of claim 9, further comprising a compressed gas passageway configured to fluidly couple a compressed gas source to the reductant injection assembly.
 16. A method of purging reductant from a reductant dosing cabinet, the method comprising steps of: coupling the reductant dosing cabinet to a reductant injection assembly that injects the reductant into an exhaust stream of an engine and to a reductant replenishment assembly that is spaced from, and external to, the reductant dosing cabinet; fluidly coupling a suction side of a pump assembly of the reductant dosing cabinet to the reductant replenishment assembly; and operating the pump assembly so as purge the reductant in both a tank of the reductant dosing cabinet that is coupled to a suction side of the pump assembly and the pump assembly to the reductant replenishment assembly.
 17. The method of claim 16, wherein: coupling the reductant dosing cabinet includes coupling a reductant discharge passageway between the suction side of the pump assembly and the reductant injection assembly; and fluidly coupling the suction side of the pump assembly includes selectively configuring at least one valve of the reductant dosing cabinet to divert the reductant away from the reductant injection assembly and to the purge passageway during the purge operation.
 18. The method of claim 16, wherein: coupling the reductant dosing cabinet includes coupling a reductant discharge passageway between the suction side of the pump assembly and the reductant injection assembly; and the method further comprises steps of: fluidly coupling the reductant discharge passageway to a reductant return passageway between the pump assembly and the reductant injection assembly; and flowing compressed gas from the reductant injection assembly through the reductant discharge passageway and the reductant return passageway so as to force reductant in the reductant discharge passageway and the reductant return passageway back to the tank.
 19. The method of claim 16, wherein operating the pump assembly includes flowing air in the tank through the pump assembly so as to force the reductant in the pump assembly to flow to the reductant replenishment assembly.
 20. The method of claim 19, comprising drawing air into a vent of the tank so as to fill a space in the cavity of the tank that was previously occupied by the reductant. 